The present legacy electrical system and power quality being delivered to users is being degraded by a number of disruptive technology and legislative impacts, especially with the rapidly increasing myriad of privately owned and operated domestic and commercial Distributed Energy Generation (DEG) devices connected at any point across a low voltage LV power distribution network. This increasing degradation in power quality being delivered to the end consumers, especially voltage volatility, current and frequency aberrations, can negatively impact the performance or even damage electrical equipment, appliances, and electronic devices connected to the electrical power system in the user premises, and can even trip and disrupt wider area LV power distribution network, substation protective equipment, high voltage (HV) transmission grids, and even generators.
Referring to FIG. 1. The legacy alternate current (AC) electrical power systems which started in the later 1800's had limited transmission capabilities due to low voltage components, and over short distances. So a myriad of separate independent power producers (IPP)'s sprang up with a central generator and supplied power to local areas or local power islands. Back then, there were a range of voltages and various frequencies for each local area or local power island. The loads were simple which comprised largely incandescent electrical lighting.
Referring to FIG. 2. As electrical technologies advanced, with HV insulators and switches, transmission voltages were allowed to be increased hence enabling the delivery of higher electrical power over longer distances. Voltage levels increased rapidly from Edison's initial 220 VDC local grids, to the first AC grids of 2.3 KVAC (1893), rising every few years to 765 KVAC (late 1960's). With longer transmission grids resulted in overlapping power islands, conflicts began in areas of business, competing technical standards, and finally monopolies emerged. With the increasing use of electrical power, questionable reliability, and growing conflicts in the electrical industry, many countries moved to legislate regulatory controls over their electrical industries.
In the United States, it became critical that the rapidly growing electrical industry be regulated to create national standards that also would allow multiple grid interconnections to create stable power networks across the country with the goal of delivering high quality reliable power to the consumers. The Federal Government in the 1992 Congress passed the Energy Power Regulatory legislation at the Federal level. So FERC (Federal Energy Regulatory Commission) was charged with regulating power quality from the central power utilities, who owned the generators, transmission, and distribution networks end to end. Then in 1996, in order to increase competition and optimize the cost of electrical power, FERC deregulated the electrical industry further and ruled that generation, transmission and distribution of electrical power must be conducted by legally separate entities. This created the competitive market for wholesale power available on the transmission grids with the generators selling and the distributors purchasing wholesale power from the transmission companies.
Many countries enacted similar deregulated competitive electrical power structures in the 1900's. In the United States, after a major North East Blackout in 1965, the NERC (North American Reliability Council) was created to maintain and enforce system standards and power quality reliability. Then again, after another major Blackout in North East and Canada Aug. 14, 2003, the Federal Government in June 2007 passed even tighter regulatory laws and penalties on the transmission operators mandated legally by the NERC working with FERC.
Referring FIG. 3. Reaching the present day, what came with the deregulation legislation was DEG, which was the ability of connecting small power generators to the HV transmission grids. With still further technology advances in power generation such as CHP micro-turbines, fuel cell installations, and especially renewable energy sources such as photovoltaic (PV), solar thermal, and wind, coupled with falling capital costs, private owners in domestic and commercial premises have stated purchasing and installing these small DEG devices.
These small privately owned and operated domestic and commercial DEG device installations accelerated with the introduction of then later updated and modified Feed in Tariff (FIT) policy over the last few years. The FIT mandates transmission operators to pay owners of DEG devices minimum prices for excess power being generated and added back into the energy grid. So now with a myriad of privately owned and operated domestic and commercial DEG devices, connected in increasing numbers to the local LV distribution networks, it is creating a large impact on power quality for not only the end consumers, but the increasing real possibility of wide area major grid disruptions. Especially with the increasing chances of a transmission grid trip due to the reduction of spinning reserves with the offloading of the large central utilities due to additional power being generated by the growing number of installed DEG devices. The resultant voltage, current and frequency aberrations from these privately owned and operated domestic and commercial DEG devices that are superimposed onto the distribution networks and transmission grids increases the possibility of setting off the system trip protective switch gear, normally adjusted to the tight tolerance and long established legacy electrical power specifications.
Furthermore, because of these increasing voltages on the distribution networks, when over the regulated voltage limits the DEG interface control electronics disables the DEG interface, it does not only shut off any DEG energy recovery from the DEG installation but also eliminates any FIT recovery for the end consumers. Hence the more DEG interfaces connect along a local distribution network, for example a neighborhood of domestic PV installations, as the distribution network voltages increase because of the amount of excess energy being delivered into the distribution network by the DEG installations, the more number of these DEG interfaces will be disabled by the DEG interface control electronics, with no energy recovery or FIT for the end consumers.
Power quality is defined under the following specifications, the key parameters being consistent and stable voltage, harmonics, and frequency of the electrical power delivered to the user. With the advent of more and more electronic devices and equipment being connected to the electrical system which are complex electrical loads, especially with the increasing power demand being domestic and commercial, rather than industrial such as in the United States, these electronic devices, since they offer more complex loads to the electrical system, they can introduce electrical power instability, and these electronic devices are generally located in domestic and commercial premises with increasing power demands from the LV distribution networks, adding to the voltage instability with changing loads and power factors across the distribution networks.
When the legacy central generating utilities owned the complete equation of generation, transmission and distribution end to end, they agreed to, and could meet, the legislated tight power quality standards specified and enforced by government and regulatory bodies. With the advent of even further de-regulation of the electricity industry in many countries, and expanding FIT, allowing the connection of an increasing myriad of privately owned and operated domestic and commercial DEG devices to the LV distribution network and increasing complex loads and changing power factors, there is an increasing critical degradation of power quality especially voltage instability and increased potential of local and large area major power disruptions.
Electrical equipment, appliances, electronics, and especially electrical motors, are all designed to perform optimally at the legislated voltage and frequency tight set legacy standards. Electrical and electronic devices subjected to these voltage and frequency aberrations, outside the set tight legacy tolerances, can malfunction, degrade performance, and even be damaged.
These power quality standards have a long history of regulatory normalization across each country, and even across the world, particularly with the advent of electrical transmission major grid connections between countries. Examples of electrical LV distribution mains standards by some countries are as follows, referencing nominal voltage, voltage tolerance, nominal frequency, and frequency tolerance, for the LV distribution network for domestic and commercial users:
NormalNominalVoltageFre-FrequencyRegu-VoltageTolerancequencyToleranceCountrylatory(VAC RMS)(%)(Hz)(%)USAFERC/120(1φ)±560±1NERC240(1φ)120/208(3φ)UKEN50160230(1φ/3φ)+10, −650±1
Many countries have similar nominal LV Distribution POU voltages such as 220/230/240 VAC (and trending this higher distribution network voltage to 230 VAC), and lower voltages generally 110/115/120 VAC, with Frequency now standard at 50 Hz or 60 Hz. Generally 50 Hz for the higher 220/230/240 VAC voltages, and 60 Hz for the lower 110/115/120 VAC voltages, but either frequency is used in some countries due to their electrical power system history. voltage tolerance can be standardized at ±5%/±6%/+10, −6%/±10%, the maximum tolerance in any country is set at ±10%.
Frequency tolerance is normally standardized in many countries to ±1%, some countries have ±2%, which is the maximum frequency tolerance allowed.
Power quality problems are associated with voltage or frequency deviating outside the specified regulatory set and enforced limits. Voltage magnitude problems can be:                1) Rapid voltage changes;        2) Low frequency voltage change causing flicker;        3) Under voltage dips (under −10%);        4) Over voltage surges (Over +10%)        5) Overvoltage spikes and noise;        6) Voltage unbalance in 3-phase system;        7) Voltage and current harmonics;        8) Power factor (PF)—the phase of the voltage and current being out of phase due to reactive power imbalance referred to as power factor (PF=1, V and I in phase, PF=0, V and I−180° out of phase) can also create not only voltage and current harmonic problems, but also electrical and electronic equipment, and especially in electrical motors, wasted power, under performance, and also possible damage;        9) Current imbalance in the 3-phase system, where each phase is loaded with unequal currents can cause transmission and distribution equipment problems and degraded power quality; and        10) Frequency deviations also can impact performance and operation of electrical and electronic devices, transformers, and electrical motors;        
Because of these increasing voltages on the distribution networks, when over the regulated voltage limits the DEG interface control electronics disables the DEG interface hence not only shuts off any DEG energy recovery from the DEG installation but also eliminates any FIT recovery for the user. Hence the more DEG interfaces connected, for example domestic houses, along a local distribution network, for example a neighborhood of domestic PV installations, as the distribution network voltages increase because of the amount of excess energy being delivered into the distribution network by the DEG installations, a significant number of these DEG interfaces will be disabled by the DEG interface control electronics, with no energy recovery or FIT for the users.
All of these power quality issues degrade the power quality being delivered to users, especially voltage instability across and through the LV distribution network at POU, where now, in addition, the myriad of privately owned and operated domestic and commercial DEG devices being connected, excess power generated by these DEG devices is being loaded back onto the local LV distribution network. Also, these privately owned and operated domestic and commercial DEG devices, even though they have to meet performance test specifications, IEC 61215 (Ed. 2-2005) and IEC 61646 (Ed. 2-2008), they can still set up widely varying Voltage, Frequency and rapid power fluctuations, on the local LV distribution network at POU. These domestic and commercial DEG devices are small PV installations, micro-wind, micro-hydro, CHP micro-turbine, CHP fuel cells, and possibly hybrid automobiles in the future. Also, these problems can also reduce the efficiency of electrical power usage in the electrical and electronic loads at the POU. For example electrical motors waste power when they are driven at a higher voltage than the electric motor was designed for optimal performance, and also excessive PF, voltage and current unbalance and harmonics can not only decrease efficiency but also can damage these sensitive electrical and electronic loads.
The large renewable industrial PV, solar thermal, wind and hydro installation need large physical areas away from population centers, the power users, hence the large industrial installations need end to end HV Transmission over generally long distances, so these large installations can be owned and controlled by the utility generator, hence can meet and be responsible for the Transmission Operator regulated power quality standards.
The advantage of the large numbers of small privately owned and operated domestic and commercial DEG devices, is the power is generated locally, close to the users or POU, through the LV distribution network. But the owners of these privately owned and operated domestic and commercial DEG devices, purchase, install and operate these DEG devices, but have no responsibility for the impact on the local LV distribution network power quality. These legacy local LV distribution networks in most cases were not initially designed for large number of domestic and commercial DEG devices to be connected. So there is real and increasing concern by the regulatory bodies, with the increasing penetration of these privately owned and operated domestic and commercial DEG devices, not only user power quality being degraded, but local power instability on the LV distribution networks. Added to this is the increasing connection of complex loads, changing power factors, and changing loads across the distribution networks. This results in increasing service disruptions over even large areas and even HV transmission grids due to voltage, current, or frequency aberrations outside the tight tolerance electrical standards that can trip voltage, current, or frequency electrical system safety and protection devices, causing electrical disruptions and outages. Also because of these increasing voltages on the distribution networks, when over the regulated voltage limits, the DEG interface control electronics disables the DEG interface; thus not only shuts off any DEG energy recovery from the DEG installation but also eliminates any FIT recovery for the user.
The electrical power industry and regulatory bodies are grappling with this new and disruptive evolution in the legacy electrical system. Suggested solutions to this increasing and real problem are all aimed at maintaining the legacy and historical transmission and distribution network structure and power quality tolerances.
One significant book, which is dedicated solely to the looming problem of increasing penetration of privately owned and operated domestic and commercial DEG devices is titled “Integration of Distributed Generation in the Power System”, authored by Math Bollen and Fainan Hussan. The content of which is incorporated herein by reference in its entirety. This book was only recently published in 2011 by IEEE, and the book represents a detailed in-depth-study of over a 10 year period, all related to the disruptive evolution of privately owned and operated domestic and commercial DEG devices on power quality.
This book has 470 references, and is excellent in its in-depth research on detail to the increasing critical aspects of the disruptive impact of DEG devices on the overall electrical power system. Many authors and institutions present similar solutions to solving this problem, the same solutions as also covered fully in detail in this book, and again all aimed at maintaining the legacy electrical standards power quality tolerances, by protecting and controlling the HV transmission grid and LV distribution networks. But again, all of these solutions suggested are solely to maintain these historical, long established over many decades, of legacy tight tolerance electrical industry standards. This deeply researched and detailed book finally concludes in its recommendations to address the critical problems of the increasing connection of larger numbers of privately owned and operated domestic and commercial DEG devices, is by adding a layer of digital communication networks to link the DEG devices back to controlling and protecting the HV transmission grids, or even this digital communication network can precipitate tripping voltage protection relays on the distribution network feeders, or even disconnecting DEG devices if say overvoltage results. The book also suggests various schemes of adding storage, and other load shifting actions based upon the added digital communication network of shifting reserves to customers or DEG devices.
The book also concludes another possible conventional solution because of the concerns of the large cost, time, and complexity involved to add the extensive sophisticated digital communication networks and software algorithms that would be required, so in their final paragraph on page 470—“Next to these advanced solutions, the classical solution of building more stronger lines or cables should not be forgotten. However, the introduction of new types of production will require use of advanced solutions in more cases than in the past. By combining the classical and advanced solutions, the power system will not become an unnecessary barrier to the introduction of distributed generation.”
So this last paragraph of the book on page 470, sums up their concerns of the increasing penetration of privately owned and operated domestic and commercial DEG devices on the LV distribution network in particular, and its potential critical impact on the stability of the overall electrical grid. They propose advanced digital communication networks and software solutions (“Smart Grid”), but also suggest a simple, but expensive, conventional physical solution in adding more copper wire to the existing LV distribution networks that will increase the power handling capability and reduce Voltage instability by decreasing the resistance of the wires in the present LV distribution networks as these DEG devices add increasing and volatile power onto the local LV distribution networks. These LV distribution networks were initially not designed, and certainly this new DEG problem, not anticipated, with this recent evolution of the connection of large numbers of privately owned and operated domestic and commercial DEG devices.
The last paragraph in this detailed book underlines clearly that:                1) All solutions suggested are aimed and still meeting the present tight tolerances of the historical legacy Regulated and enforced electrical standards for power quality;        2) Connection of large numbers of privately owned and operated domestic and commercial DEG devices to the local LV distribution networks is a major problem, as the LV distribution networks were not initially designed to handle this new disruptive electrical evolution, hence the suggestion of physically upgrading these LV distribution networks underlines the complexity of this real and critical problem;        3) The book's last line suggests, because of the complexity and cost and time for these advanced complex “digital” solutions (“Smart Grid”), that just adding additional copper wires to the present LV distribution network will help. But that is also a very expensive solution, to upgrade physically the LV distribution networks, and will take many years to complete;        4) With these critical problems now happening with the degradation of power quality and possible widespread Transmission grids tripping, there may be legislative moves to limit the number of privately owned and operated domestic and commercial DEG devices allowed to be installed;        5) The book also has no suggestion on who would be responsible for the costs of the huge digital communication software network and who has final responsibility for power quality delivered to the user; and        6) Again, the book, and all suggestions in the industry, surrounding this recently evolving DEG devices problem, is the underlying, totally accepted without question, in maintaining the historical, legacy, Regulated power quality tight specifications and framework, and still meeting the decades old legacy electrical system power quality tight tolerance standards.        